Emergency Authorities Under the National Emergencies Act, Stafford Act, and Public Health Service Act [June 3, 2020] [open pdf - 1MB]
From the Summary: "The Supreme Court has explained that the President's authority 'must stem either from an act of Congress or from the Constitution itself.' Because Article II of the Constitution does not grant the Executive general emergency powers, the President generally must rely on Congress for such authority. Congress has historically given the President robust powers to act in times of crisis. These emergencies powers are scattered throughout the 'U.S. Code' and touch on matters ranging from international emergencies to public health crises to natural disasters, among many other things. Many of these authorities are triggered from declarations made under three frameworks: the National Emergencies Act (NEA), the Robert T. Stafford Disaster Relief and Emergency Assistance Act (Stafford Act), and the Public Health Service Act (PHSA)."
CRS Report for Congress, R46379
Congressional Research Service: https://crsreports.congress.gov/